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GLIN==> Avon Point, Lake Erie, research update
- Subject: GLIN==> Avon Point, Lake Erie, research update
- From: aa4532@lcfn.org (John Lavelle)
- Date: Sun, 15 Aug 1999 16:47:36 -0400
- List-Name: GLIN-Announce
- Reply-To: aa4532@lcfn.org
August 14, 1999
John Lavelle
346 Inwood Blvd.
Avon Lake, Ohio 44012
E-mail aa4532@lcfn.org
Some quick notes on what is happening at Avon Point,
a shale reef in the Central Basin of Lake Erie between
the cities of Lorain and Cleveland Ohio. This a continuation
of two other notes posted on the GLIN-announce.
I have not made as taken as many bottom samples this
year as in previous ones for two reasons: One, the Lake
has been rough (higher waves) then in previous years and
the amount of detritus and plankton has also been much
greater. Two, I've now been able to use a boat to go
off shore with and it is a learning process in how
to dive and take the samples from the boat (also I am
trying to teach myself underwater photography which
contributes to having less time for sampling).
From a qualitative stands point this is what is
happening on the reef to the middle of this year.
The sponges have not appeared on the rock's surfaces
this year and only two small (about 5 cm2) brown sponges
have been seen on the rock's bottom surfaces. I think this
may be due to the increase in detritus and plankton in the
water than in any year so far.
The rounded gobies are as plentiful as ever (about 10
to 15 per square meter on the rocky areas of the reef,
though this number is hard to verify because the gobies are
attracted by my presence and tend to swarm around me when
I am on the bottom. There are few full grown ones but
pentiful little ones.
The ablabsymia (midges) population appears to have
shot way up based on viewing the number of nests on the
rock's undersides. This too may be a result of the increased
plankton load>
The Cladophora has been thicker and has lasted much longer
than in previous years.
The bryozoan, F. Sultana is still common but not as
common as last year.
No snails have been seen at all this year.
Very few planarians have been found.
The number of hydras found in the late Spring and early
Summer are still at very low numbers compared to the early
years of this study.
COPEPODS FROM 1993 TO 1999, AVON POINT
The samples so far this year for the crustacean copepods
for this area of the Lake give mixed readings. Whereas the
Calanoid copepods have seemed to have leveled off at low
numbers the cyclopoids have shown an increase in numbers.
Interestingly though the Nauplii of both families show a
decrease in numbers.
COPEPODS
Monthly Averages for Copepods
The following data is based on 12.5 liter samples taken twice
a week. All the samples where taken in the morning from the
same location.
Calanoid Copepods 1993 to 1999
1993 1994 1995 1996 1997 1998 1999
Jan. 17.2
Feb. .29
Mar. 2.2 2.6 .9 1.56 .25
Apr. 7.7 3.7 3.5 4.5 24.1 2.9
May 104.3 84.8 37 40.5 11.6 15.2
June 12.75 71.4 56.7 60.7 *144 27.8 26.7
July 4.85 22.4 2.4 28.4 8.5 4.6 8.1
Aug 4 16.7 5 28.1 7.1 2.6
Sept 26.57 32.1 13.6 6.8 11 12
Oct 15.55 11 9.3 34.6 6.3 21
Nov 9.11 9.9 5.3 2.9 4.9 14.3
Dec 5.57 6.3 7.2 5.6 .8 20.1
Average of the 31.3 20.9 23.04 25.3 15.34
Calanoids Apr. thru Dec.
1994 to 1998
* Except for the extraordinary number of animals found on one
sampling date the number of calanoid copepods would have shown
a marked decline in 1997. That date was June 15. The sample
had the extraordinary number of 880 calanoids in the 12.5 liter
sample. The total number of calanoids found for the entire year
in about 50 samples minus the June 15 date was 1130, thus the one
sample had more animals than all the samples for the entire
year. I have belabored the point of the nonrandomness of the
zooplankton in the 1996 report and so will not cover that ground
again. What I want to point out here is that if the June 15 sample
is dropped from the reporting than the copepods had a steep
drop in their numbers in 1997 and the average for the month of
June would be 52 per sample rather than 144 per sample. The
average for the year would drop from 25.3 per sample to 11.4
per sample. Whether this dropping of the sample from the total
counts is valid I leave up to the reader but if the June 15
sample is ignored than the calanoids have had a major decline
in 1997.
Cyclopoid Copepods
The table does not include the cyclopoid T. Mexicanus pranis.
This small copepod was found very sporadically in the samples
until this year. Though when it was found it could be found
in large numbers.
Comparison of Cyclopoids Copepods from 1993 to 1999
1993 1994 1995 1996 1997 1998 1999
Jan. 3
Feb. 2.3
Mar. 1.4
April 8.6 9.77 3 .3 2.1 2.4
May 38.33 56.75 50.33 8.9 34.7 24.6
June 51.5 38.77 182 109.36 35.4 59.1 89.2
July 25 26.6 19.55 17.13 30.2 6.3 111.4*
Aug. 38.5 13.7 19.11 5 7.7 3.7
Sept. 17.28 12.5 7.12 17.33 2.9 1.2
Oct. 8.55 13.1 3.77 8.88 2.3 3.4
Nov. 12.88 7.7 5.66 1.5 4.3 1.6
Dec. 10.71 5.13 4.4 7.66 1.1 3.3
Average for the 18.277 34.23 24.46 10.3 12.82
years 1994 to 1998
Apr. to Dec.
*The average for July, 1999 is skewed by one sampling date (July 14)
which a total of 638 cyclopoids in the sample. Eliminating the
one sample from the average for the month gives a new monthly
average of 23.7.
A further note on this sample. After taking the plankton
sample from off the jetty I went out in a boat about a 1/2 mile
from shore to get the benthic sample in about 15 feet of water.
The number of cyclopoids in that 5 liter sample was 184.
Multipling this by 2.5 to make it equal the plankton sample gives
a total of 460. Meaning this massing of cyclopoids in the area
probably covered a large area. The cyclopoids totals taken from
each sample for the month of July were:
July 5 45
8 21
11 1
14 638
21 60
25 7
28 8
Avg 111.4
Copepod Nauplii
No attempted was made to distinquish between cyclopoid and
calanoid copepods.
Nauplii
Monthly averages
1993 1994 1995 1996 1997 1998 1999
Jan. 3.25 3.8 0.3 0.4
Feb. .75 1.9 1.4 .29
Mar. 9.5 1.4 .9 .25
Apr. 36.16 28 8.25 61.3 33.4 36.8
May 133.97 161.25 63.55 13.8 53.4 20.1
June 13 61.3 129.44 121.22 64.8 38.5 17.1
July 2.71 27.66 29.4 51 48.6 5.2 4.4
Aug. 4.5 49.55 70.44 30 15 9.8
Sept. 6.57 26 40.12 49.66 10 38.4
Oct. 4.77 10.22 13.11 44 8.8 14.8
Nov. 6.44 2.88 4.44 1.625 2.8 1.4
Dec. 4.57 5.62 2.4 1.66 .2 .25
Yearly average 39.26 53.17 41.21 25.03 16.26
from Apr to Dec.
ROTIFERS AT AVON POINT
This too is a continuation of the report posted on the
GLIN - annouce awhile back. I have not here broken out the
rotifers by genus as I did in the second posting on the GLIN.
Even with the lumping together of all the rotifers it can be
easily seen that for some reason the rotifer numbers have been
cut more than in half from what they were in previous years.
I know very little about these little critters and therefore
will not even hazard a guess as to why their population has
fallen so.
Plankton sample size 12.5 liters
In the chart below the number column is the total
number of all rotifers found in the month. The average
is the total rotifers divided by the total number of
samples taken that month. Generally there were two samples
taken every week or 8 to 9 samples a month
1994 1995 1996
number average number average number average
April 60 10 75 8.33 250 31.25
May 78 8.6 660 82.5 *1362 151.33
June 532 48.36 491 54.55 1335 148.33
July *4144 460.44 501 55.66 2787 348.37
Aug 2065 229.44 176 19.55 2697 385.28
Sept 124 15.5 379 47.38 1217 135.22
Oct 82 9.11 279 31 267 29.66
Nov. 66 7.3 102 11.33 103 12.87
Dec. 1 .12 3 0.6 10 1.11
1997 1998 1999
number average number average number average
Jan 13 2.2 3 0.5 1 .02
Feb 0 0 4 0.6 0 0
Mar 6 .7 3 0.3 4 .057
Apr. 36 4 310 38.8 208 26
May 726 38 2594 324.3 1009 112
June 2229 247.7 1274 141.6 593 65.9
July 1271 141.2 1610 178.9 151 21.6
Aug. 707 101 1793 224.3
Sept 1245 155.6 970 121.5
Oct. 759 84.3 925 102.8
Nov. 11 1.2 37 4.1
Dec. 3 .3 2 .25
* The July 1994 and the May 1996 are so high because in
both these month on one date there was an enormous
number of rotifers.
July 20 1994 there were 3043 rotifers in just one 12.5
liter sample.
May 26 1996 there were 1073 rotifers in the sample.
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